The invention relates to a starting unit for use in drive systems, in particular for use in transmissions of vehicles, specifically having a hydrodynamic coupling and a lockup clutch.
Transmissions for use in vehicles, in particular in the form of automated manual transmissions or automatic transmissions, are known in a wide range of designs. A common factor of these variants is generally that the starting operation is effected by means of a clutch element in the form of a friction clutch or of a hydrodynamic converter. To effect power transmission in the other gear ratios, mechanical speed/torque conversion devices in various designs are generally connected downstream of these starting units. To avoid the introduction of torsional vibrations into the drive train, in particular into the transmission unit, there are generally devices for vibration damping, for example in the form of a torsional vibration damper, which are connected upstream of the transmission unit or are integrated in the latter in the region of the transmission input shaft. However, known integrated solutions involve the use of a vibration damper which is used only to compensate for or shift vibrations or additionally operates according to the friction damping principle. However, solutions of this type do not always give satisfactory results; in particular, stick-slip effects mean that it is impossible to completely rule out excitation of vibration during critical operating states of the drive train. A further drawback is that the intensity of damping achieved by damping devices of this type cannot be varied, or can only be varied with a very high level of outlay, over the operating range. Furthermore, the increasing demands with regard to environmental protection aimed at reducing emissions mean that the hydrodynamic converter in the transmission unit has to be closed earlier, with the result that the vibration excitation is considerably increased.
The invention is therefore based on the object of further developing a starting unit for a transmission unit for use in drive systems of vehicles in such a manner that vibration excitation is avoided in virtually any operating state, and its damping performance allows the possibility of adjustment. The space taken up is to be minimal, and the entire starting unit is to be suitable for achieving a high degree of standardization. Furthermore, it is to be distinguished by a low outlay on design control and is to be easy to integrate into the drive system or a force transmission unit, for example in the form of a geared transmission unit.
The solution according to the invention is described below.
The starting unit comprises a starting element in the form of a hydrodynamic speed/torque converter and a lockup clutch, the output sides of which are at least indirectly connected to one another in a rotationally fixed manner. Furthermore, there is a device for vibration damping, comprising at least one torsional vibration damper with hydraulic damping.
The torsional vibration damper is preferably connected functionally downstream of the lockup clutch, during force transmission in traction mode as seen from the drive to the output of the starting unit. The output ends of lockup clutch and speed/torque converter are for this purpose at least indirectly connected to one another in a rotationally fixed manner. In addition to the fact that a torsional vibration damper with hydraulic damping operates without wear, its use in a starting unit in a drive train offers the advantage that, on account of the avoidance of the sticking phases which are present when using a mechanical damping device in the form of a friction damper, excitation to vibrate can be virtually ruled out over the entire operating range. It is easy to adjust the damping intensity by means of the viscosity of the damping medium used or by varying the gap geometries, involving very little outlay. The damping which is established is also proportional to vehicle speed, which means that high frequencies or high amplitudes lead to a high level of damping.
The device for vibrational damping preferably comprises only one torsional vibration damper with hydraulic damping. In the installed position, during force transmission in traction mode, and as seen from the drive, the device for vibration damping, or at least the torsional vibration damper, is arranged:
a) spatially in front of the hydrodynamic speed/torque converter and behind the lockup clutch, or
b) spatially in front of the hydrodynamic speed/torque converter and in the same plane as the lockup clutch, or
c) spatially in front of the hydrodynamic speed/torque converter and the lockup clutch, or
d) spatially behind the hydrodynamic speed/torque converter and the lockup clutch.
In a particularly advantageous configuration of the starting unit, the device for vibration damping, in particular the torsional vibration damper with hydraulic damping, is part of the lockup clutch.
The torsional vibration damper with hydraulic damping functions as a highly elastic clutch, i.e. a clutch with a low rigidity for torque transmission between the drive of the starting unit and the output. The torsional vibration damper with hydraulic damping comprises a primary part, which can be at least indirectly coupled in a rotationally fixed manner to the drive or the output of the starting unit, and a secondary part, which can be at least indirectly coupled to the output or the drive, it being possible to couple the primary part and secondary part to one another by means of at least one damping coupling and spring coupling. For this purpose, there are first means for effecting a spring coupling and further second means for effecting a damping coupling, a functional division between the means for effecting the spring coupling and the further, second means for effecting the damping coupling preferably being provided. It is also conceivable for the functions to overlap. The means for spring coupling are used to effect the function of an elastic clutch. However, the term spring coupling is not to be understood as meaning only connection options using spring devices, but also any connecting elements which have a spring characteristic or an elastic behavior. The first means for effecting the spring coupling and the second means for effecting the damping coupling are preferably arranged in separate chambers which are arranged spatially apart from one another and are formed between the primary part and the secondary part. The means for effecting the damping coupling comprise at least one chamber which can be filled with hydraulic fluid and/or another damping medium and which in turn may be assigned means for influencing the damping performance. However, designs with an at least partial functional overlap between the means for spring coupling and the means for damping coupling are also conceivable.
The means for influencing the damping performance preferably comprise at least one throttle point which is assigned to a damping chamber and is integrated in the device for vibration damping or the torsional vibration damper with hydraulic damping. It is preferable for the throttle point to be arranged directly in the damping chamber.
An embodiment of a torsional vibration damper which is particularly compact and reliable in terms of its operation also comprises further, third means for limiting the twisting angle between primary part and secondary part, which are assigned to the damping chamber and divide the damping chamber into at least two part-chambers, which are connected to one another via at least one throttle point, the third means being involved in the formation of the throttle point. The following options exist in connection with the formation of the throttle point:
a) Integration of the throttle point in the third means;
b) Formation of the throttle point between the third means and the spatial limits of the damping chamber formed by the primary part and the secondary part.
This embodiment allows the damping performance to be influenced automatically by influencing the quantities of damping media which are contained in the individual part-chambers and are effected when the primary part rotates in the peripheral direction with respect to the secondary part. For this purpose, the third means are arranged fixed in the peripheral direction either on the primary part or the secondary part, and extend into the damping chamber. The third means may comprise, for example, at least one projection which is arranged on the secondary part and engages in cutouts in the primary part, in the peripheral direction in the installed position, in such a manner that the projection can be displaced relative to the primary part. The cutouts on the primary part, in the peripheral direction, then form a stop for the projection of the secondary part. In a similar way, the projection may also be formed on the primary part and may engage in the recesses on the secondary part which are required to form the damping chamber. For torque transmission, at least one compression spring device, which is preferably arranged and becomes active in the peripheral direction, is provided between the primary part and the secondary part. Furthermore, means for damping rotary vibrations, which counteract movement of the primary part relative to the secondary part and which, through the relative movement of the primary part with respect to the secondary part, convert work performed by the thrust forces into heat, for example, are arranged between the primary part and the secondary part.
In a further advantageous embodiment, there is provision for the damping medium to be introduced in the region of the device for limiting the twisting angle. It is also possible for the space between primary part and secondary part to be completely filled, in addition or by taking over responsibility for the function of the damping chamber.
Hydraulic fluid as damping medium can be supplied on a one-off basis from the outside, can be supplied during operation one or more times or the supply can be effected by exchange via a hydraulic-fluid supply system. Furthermore, the supply can be effected on a one-off basis by means of a separate operating-medium supply device, i.e. by means of dedicated damping filling, or directly from the unit which is to be damped, via corresponding supply lines. In this context, it is also conceivable to form a circuit which enables the hydraulic fluid to be kept at a constant temperature at all times. In this case, it is even possible to use hydraulic fluids of lower quality as damping medium.
The lockup clutch is preferably a mechanical clutch of disk design which is in the form of a wet multidisk clutch. This means that the disks run under wet conditions. This is easy to achieve by the operating medium located outside the working space of the hydrodynamic speed/torque converter simultaneously being used as lubricant for the lockup clutch. This is generally operating medium which has accumulated in the operating-medium sump of the converter or in a storage chamber. In this case, there is no need to provide additional sealing measures between converter and lockup clutch, and the lockup clutch can easily be integrated in the housing of the converter, in which case an operating-medium supply source can be used for two different functions, namely the function of the hydrodynamic converter as a starting element and the lubrication of the lockup clutch. This results in a structural form of a wear-free starting element which is particularly compact in terms of its structure and functionality.
An advantageous further development of the above embodiment consists in the damping medium for the torsional vibration damper also being formed by the operating medium of the converter or the lubricant of the lockup clutch.
A particularly advantageous configuration of the starting unit consists in the function of the clutch input or output disk of the lockup clutch being assigned to an element, primary part or secondary part of the torsional vibration damper, so that it is possible to achieve a particularly compact design of the starting unit with regard to the overall length required. The number of connections to be produced between the individual elements is greatly reduced. It is preferable for the primary part to form the clutch output disk of the lockup clutch and for the secondary part to be connected to the turbine part of the hydrodynamic speed/torque converter.
In a further, particularly advantageous configuration, to more finely tune the damping performance to the individual operating ranges in the interior space, which is filled with a damping medium, between the two components primary part and secondary part, what is known as a floating damping ring is provided, which is not connected in a positively-locking manner to either of the two masses. This floating damping ring forms at least one first displacement chamber with a first component, for example the primary part or secondary part, and forms at least one second displacement chamber with the second component, i.e. the secondary part or the primary part. In this way, the floating damping ring is exposed to a free play of forces during the relative movement of primary part and secondary part, during which it can in each case be rotated to a limited extent with respect to each of the two components. Taking account of the fact that the floating damping ring is supported by the damping medium and also of the available gap cross sections, it is then possible for only one displacement chamber to be active in the damping in the event of low vibration amplitudes. The damping is in this case deliberately maintained at a low level, in order to achieve the required damping isolation. In the event of high damping amplitudes, in particular including in the event of a relatively low damping frequency, the second displacement chamber is active, specifically whenever the limited rotatability of the floating damping ring with respect to one of the two components has been fully utilized and the ability of the floating damping ring to rotate with respect to the other component is still available. On account of the gap geometries, the damping in this range is kept at a high level, in order to greatly damp relatively high vibration amplitudes. The damping ring itself may be of single-part design or may be of multipart design, as seen in the peripheral direction.
The lockup clutch and hydrodynamic speed/torque converter are preferably connected in parallel, but are never in joint use or engagement. The advantage of an arrangement of this type is that it is substantially only possible to differentiate between in each case two states with regard to the power transmission from the drive to the output, the power transmission taking place either purely mechanically from the drive of the starting unit via the lockup clutch to the output of the drive unit or hydrodynamically via the hydrodynamic speed/torque converter. By suitable actuation of the hydrodynamic component, this allows the advantages of hydrodynamic power transmission for certain driving states, in particular for the starting state, to be fully exploited. This can take place completely without wear, while in all other driving states a complete lockup is produced.
The integration according to the invention of the device for vibration damping, comprising at least one torsional vibration damper with hydraulic damping action, in the starting unit makes it possible to create a multifunctional drive component which takes up little space, these elements preferably being integrated in a common housing. The common housing used in this case may be
a) the housing of the hydrodynamic speed/torque converter, or
b) a housing of the connection elements, in particular of the lockup clutch, or
c) the housing of the power transmission unit, in particular of a transmission.
In cases a) and b), it is possible, according to a further advantageous configuration of the invention, to create a modular unit, which can be handled independently, comprising a drive end and an output end.
The specific design embodiment of the torsional vibration damper with hydraulic damping is left up to the person skilled in the art and depends on the particular requirements in use.
The coupling of the output end to the connection elements, for example a speed/torque conversion device of a power transmission unit, in particular of a geared transmission unit, especially the mechanical transmission part of a geared transmission unit, and of the drive end of the starting unit to the transmission input shaft or to the driving engine or some other element arranged between the driving engine and the starting unit is effected by a non-positive and/or positive lock. In the most simple arrangement, the entire modular unit is fitted onto the transmission input shaft or, if the transmission input shaft is formed by the drive end of the starting unit, onto the input of the following transmission means, in the case of geared transmission units the downstream speed/torque conversion device. Other embodiments for producing a rotationally fixed connection between the drive of the starting unit and the transmission input shaft are conceivable and are within the ability of the appropriate person skilled in the art.
There are also a wide range of options with regard to the design of the lockup clutch. It is generally designed as a mechanical friction clutch, preferably of multidisk design. In this case, it comprises at least one clutch input disk and a clutch output disk which can be brought at least indirectly into operative connection with the clutch input disk and which is connected in a rotationally fixed manner, at least indirectly, i.e. either directly or with further transmission means in between, to the output of the starting unit. If the device for vibration damping is designed as part of the lockup clutch, the clutch output disk is formed by the device for vibration damping. In this case, the coupling to the output of the starting unit is effected via the device for vibration damping, which is connected in a rotationally fixed manner to the output of the speed/torque converter, in particular the turbine wheel.
The rotationally fixed connection between the output ends of the hydrodynamic speed/torque converter, in particular of the turbine wheel and of the lockup clutch, can be effected releasably or non-releasably in terms of mounting. The connection itself may in the former case be of positively and/or non-positively locking design. In the second case, the rotationally fixed connection is effected either by material-to-material bonding or by a design as an integral unit of the turbine wheel of the hydrodynamic speed/torque converter and output of the lockup clutch, i.e. of clutch output disk. The type of connection is selected according to the design which is to be used for the hydrodynamic speed/torque converter and/or for the lockup clutch and the specific requirements in use. This statement also applies, in a similar way, to the production of the rotationally fixed connection between the device for vibration damping and the output or, when the clutch output disk of the lockup clutch is designed in the form of the device for vibration damping, to the connection between the device for vibration damping and the hydrodynamic speed/torque converter.